There exist several methodologies by which flashlight battery power can be determined and displayed to the user.
Prior art as shown at the U.S. Patent Office. A simple Boolean search term of abst/(flashlight and battery and (indicator or life)) elicited two meaningful results: U.S. Pat. No. 4,962,347—Flashlight with battery tester and U.S. Pat. No. 4,876,632—Flashlight with battery life indicator module.
Both of these approaches to the problem are conventional and utilize some derivative of Ohm's Law; they impose some load upon the battery, measure current flow through that load or voltage across the battery, and from those data (load and either current or voltage) estimate the battery's probable remaining capacity. These patents were evaluated and found to reflect none of the features and capabilities of the present invention.
There are many other battery-powered portable devices that do include battery life indicators of varying types, but in a market search none was found that operates on the principles set forth herein, and none was found that cost-effectively solves the portable flashlight requirement addressed by the present invention.
There are many existing designs, products, and patents that in some ways are related to the present invention, or that in some ways attempt to solve the problem addressed by the present invention, but no reasonable combination of the terms that would reasonably discover the present invention, and no search in applicable markets, have identified a similar solution.
The term “flashlight” applies to a spectrum of handheld portable lighting products ranging from simple household convenience and safety devices to those designed to meet urgent and often emergency requirements. Some flashlight products sell for the equivalent of 30 minutes' work at minimum wage, while others cost the equivalent of an hour of a competent attorney's time, and a few exotic flashlights cost thousands of dollars.
All portable “flashlights” are powered by batteries, ranging from primitive carbon-zinc cells to cells using expensive rechargeable (nickel-metal-hydride, nickel cadmium, lead acid, lithium-ion, lithium-polymer, etc.) technologies. The best non-rechargeable flashlights use lithium-ion cells with excellent power densities, usually intended for use by law enforcement, military, and emergency services personnel, but also bought by consumers willing to pay high prices for quality and performance. Makers of such lights include Streamlight, Surefire, and Pelican.
Despite at least two patents describing methodologies by which the power remaining in a flashlight's battery can be measured and displayed, there are virtually no flashlights sold today with any sort of battery life indicator. The reason is that the prior art solutions work on battery technologies that suffer a steady decline in output voltage under load, and such voltage-under-load is an unreliable predictor of remaining life.
Existing technologies by which battery life is measured impose a temporary load on the battery and measure voltage under that load, however this practice dissipates battery power into that load and therefore the remaining life is diminished by the battery power expended in the measurement process itself.
Further, inexpensive flashlights are not designed for emergency use, and therefore compete based upon price. They use inexpensive batteries that fit the profile for which such a prior art solution was designed, but the inclusion of such a feature will raise the price of this category of product beyond the range of the market.
The expensive flashlights that are designed for emergency or tactical use employ expensive batteries (i.e. lithium-ion) and/or regulation, such that the output of the power system is relatively constant until just before the battery supply is completely depleted, at which time it dies quickly. If the prior art solutions (measuring voltage under load) were to be applied to this type of flashlight, they would show maximum remaining battery life even if the flashlight were close to the end of its life.
Therefore, modem flashlights designed either for consumers or for emergency services do not include a battery life indicator.
Products for both categories of use seem to run out of power when they're most needed, especially in emergency situations. There exists no mechanism by which a police officer, for example, can glance at a tactical flashlight and see in a moment the remaining life in the existing battery pack. And in an emergency, replacing batteries—even if spares are carried—is time consuming and sometimes not even possible.
While many of the prior art flashlight battery status measurement and display solutions may be suitable to one degree or another for the particular limited requirements they address, they are not optimum or generalized solutions for today's consumer flashlight products because those solutions are too costly to implement at the consumer level, and the consumer market is price-driven. Such battery status measurement and display solutions may be suitable to flashlights designed for emergency uses, but only if those flashlights employ carbon-zinc, alkaline, or lead-acid batteries, the output voltage of which under load correlate roughly with remaining capacity.
In these respects, the FLASHLIGHT BATTERY LIFE INDICATOR, according to the present invention, substantially departs from the concepts and designs of prior art. In so doing, the present invention provides unique advantages to certain consumer flashlights because it is economical to implement, and unique advantages to flashlights designed for emergency, law enforcement, and military usage, because it provides the user with a constant always-on display of remaining battery life in minutes.
In view of the foregoing disadvantages inherent in common flashlights, and the known methods and practices for the measurement and display of battery life in flashlights, the present invention provides a substantial divergence from custom to achieve the primary goal of providing a method by which a flashlight's remaining battery life can be constantly displayed, in the most useful format: minutes.
The main objective of the present invention is to provide a cost-effective battery life indicator for flashlights that employ batteries and/or regulated supplies with a relatively flat depletion curve.
Another objective is to provide a simple method by which a known depletion period (runtime) of a selected design or combination of components (bulb plus battery pack) can be built into the product.
Another objective is to provide a circuit by which the absence/presence (therefore replacement) of the battery pack can be sensed, triggering a reset to the preset runtime figure.
Another objective is to provide a means by which the preset runtime period can be manually adjusted by the user, based upon experience or knowledge, thus improving the accuracy of the display.
Another objective is to provide an optional nonvolatile memory, such that previous adjustments are “remembered” from one battery change to another.
Another objective is to provide an optional internal/integrated long-life battery, such that selected circuitry comprising the present invention can be self-powered, and memory components thereof can “remember” previous history and runtimes.
Another objective is to provide an always-on display, such that at any time the user can glance at the unit and determine the minutes remaining on the internal battery or charge.
Another objective is to use well-understood and inexpensive countdown timer circuitry, logic, and liquid crystal displays already in wide use, to reduce the cost of implementation of the present invention.
Another objective is to provide the potential to fully exploit the well-understood and inexpensive existing circuitry by embedding a complete (self-powered) timekeeping device in the flashlight, with the countdown feature as but one function thereof.
Another objective is to provide the potential for a simple algorithm that correlates power used with time on, with the understanding that duty cycle has an effect upon the total output minutes (runtime) of many battery types.
Another objective is to provide the potential for a means by which different power levels, selectable by the user, can be accommodated by the circuitry embodying the present invention.
It is the intention of the inventor that these objects apply to flashlight/cell combinations in which a display of either accumulated or remaining runtime is based upon a known value to which runtime on a given set of cells or charge is compared. They are specifically applicable to all flashlight and cell configurations involving an electromechanical mechanism by which a battery supply with a relatively flat depletion curve and therefore a predictable life under load (as with lithium-ion or any supply that is regulated) can be correlated with time used and therefore time remaining, and the result is displayed in a manner convenient to the user.
It is also the intention of the inventor that these objects apply to other battery-operated devices the users of which would benefit from a display of minutes remaining or percentage of battery remaining.
Other objects and advantages of the present invention will become obvious to the reader and it is intended that these objects and advantages be within the scope of the present invention.
To the accomplishment of the above and related objects, this invention may be embodied in the forms illustrated in the accompanying specification and drawings. However, the specification and drawings are illustrative of the basic concepts only, there are many possible configurations and derivatives lying within the intended scope of the invention.